Methylolated ureidopyrimidone modified regenerated cellulose product and process forpreparing same



United States Patent 3,329,519 METHYLOLATED UREIDOPYRIMIDONE MODI- FIED REGENERATED CELLULOSE PRODUCT AND PROCESS FOR PREPARING SAME Alan R. Mills, Oakland, Calif., assiguor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 6, 1965, Ser. No. 493,563 Claims. (Cl. 106165) ABSTRACT OF THE DISCLOSURE The tensile strength of regenerated cellulose products are improved by adding a methylolated ureidopyrimidone during the preparation of said cellulose or to the finished product thereof.

This invention relates to a process for improving the physical properties of regenerated cellulosic products. More particularly, the invention relates to a process for improving the tensile strength, particularly the wet strength properties, of regenerated cellulose materials such as cellophane, rayon and the like.

Specifically, the invention provides a new and highly efficient method for improving the tensile strength, particularly the wet tensile strength, of regenerated cellulose materials which comprises contacting said regenerated cellulose materials with a methylolated ureidopyrimidone as more particularly described hereinafter.

The making of synthetic fibers such as rayon from regenerated cellulose is well-known in the cellulose or viscose art. Techniques for making synthetic film materials such as cellophane from regenerated cellulose is also wellknown in the art.

Regenerated cellulose products, such as rayon and cellophane products, generally lack the dry strength needed for many applications. It is known, for example, that cellophane films are easily torn once the initial tear has been made. It is also known that the films are sometimes quite brittle and lack the softness required for certain uses. It is further known that ordinary viscose rayon has only 50 to 80 percent of the strength of silk and loses 50 to 60 percent of its strength when wet. This significant reduction in wet strength can be reduced if the spinning is carried out under tension while the filaments still are plastic with orientation of the molecule taking place. This step, however, is expensive due to the special equipment required. There is therefore a need to improve the wet strength of rayon fibers without such an expensive process or to improve further rayon produced by the above spinning under tension.

Likewise, cellophane exhibits poor wet tensile strengths. In order to make the cellophane waterproof it is customary to coat the sheet film with a wax and/or nitrocellulose lacquer. There is a further need to improve the bonding of the nitrocellulose lacquers to the cellophane.

Accordingly, it is a primary object of the present inven tion to provide a process for improving the tensile strength properties of regenerated celluose materials. It is another object to provide a process for improving the wet tensile strength of regenerated cellulose materials such as rayon and cellophane. It is a further object to provide a process for improving the bonding of waterproofing materials such as nitrocellulose lacquers to rayon and cellophane. Other objects will become apparent to one skilled in the art.

It has been unexpectedly discovered that the wet and dry strength properties, i.e., tensile strength, of regenerated cellulosic materials may be significantly improved by contacting said regenerated cellulosic materials with certain methylolated ureidopyrimidones.

Patented July 4, 1967 The methylolated ureidopyrimidones may be applied by any suitable means such as dipping, spraying, painting and the like to the formed or finished fiber or film. It is preferred, however, to add the methylolated ureidopyrimidones to either the xanthate bath wherein the cellulosic materials are somewhat soluble or to the regenerating or coagulating bath.

The manufacture of regenerated cellulosic materials such as rayon and cellophane do not form a part of the present invention. Briefly, however, viscose rayon manufacture is based upon the reaction of the hydroxyl groups of cellulose with carbon disulfide in the presence of sodium hydroxide to give xanthates which are soluble in water. Thus, alkali cellulose (obtained by reacting high alpha-cellulose sulfite pulp or cotton linters with a strong solution of sodium hydroxide, usually of 15% to 20% concentration, at a temperature between 15 C. and 20 C.) is treated with carbon disulfide (30 to 40% by weight of the dry cellulose). An orange-colored crumbly product is formed which is then dissolved in a 3% sodium hydroxide solution to give the viscous solution known as viscose in which the cellulose molecule has been degraded to an average chain length of 400 to 500 C units. The solution initially is unstable and the viscosity drops rapidly during the first day of standing. Spinning of the solution is carried out after considerable hydrolysis has taken place and the solution has ripened for 4 or 5 days. The filaments from the spinneret are passed through a coagulating or regenerating bath containing suitable coagulants such as sulfuric acid, sodium bisulfate and the like and additives, which coagulate the cellulose by xanthate hydrolysis to give a regenerated cellulose fiber. After coagulation and twisting of the filaments into a thread the rayon product is thoroughly washed and sometimes bleached. The viscose xanthate solution is converted into cellophane by extruding through a slot in the coagulating bath.

The additives used in preparing the modified regenerated cellulose materials include the methylolated ureidopyrimidones. These may be represented by the following formula:

wherein n is 0 to 5, Y is oxygen or sulfur, R is hydro gen or an alkyl radical and X is hydrogen, alkyl or alkyloi group.

Examples of the above-described methylolated ureidopyrimidones include, among others,

3 tetrahydro-2-pyrimidone, 1,3-dimethylol-4- (N,N"di-methylolthiouredio -6- cyclohexyl-tetrahydro-2-pyrimidone.

These compounds are preferably prepared by reacting urea or thiourea with the desired unsaturated aldehydes, such as acrolein, crotonaldehyde, alpha-methylacrolein, alpha-phenylacrolein and the like, and then reacting the resulting product with formaldehyde. The reaction of the urea with the unsaturated aldehyde is preferably accomplished in an acidic aqueous medium. Preferred pH range is from 3 to 5. This is accomplished by the addition of acids, such as phosphoric acid, sulfuric acid, acetic acid and the like. The amount of the urea and the unsaturated aldehyde may vary over a wide range. Preferred amounts vary from about 0.5 to 1.5 moles of the aldehyde per mole of the urea. Particularly preferred amounts of reactants vary from 0.5 to 0.7 mole of aldehyde per mole of urea. This reaction is preferably accomplished at temperatures ranging from about C. to 50 C.

The reaction of the condensate with formaldehyde is accomplished in the presence of an acid medium or basic medium, but preferably in an acid medium. This may be done by retaining the condensate in the same reaction medium and adding the amount of formaldehyde desired. Preferred amounts of aldehyde vary from about 1 to moles of formaldehyde per mole of the condensate. Especially preferred amounts of formaldehyde vary from about 2 to 4.5 moles per mole of condensate. This reaction is preferably accomplished at temperatures ranging from about 75 C. to 85 C.

The methylolated products can be used in the aqueous medium in which they are formed or they may be recovered in pure form by evaporation, distillation and the like.

The preparation of the methylolated ureidopyrimidones by the above process is illustrated below:

1,3 dimethylol 4 ureido-tetrahydro-Z-pyrimidone (A).2 moles of urea was combined with 1 mole of acr-olein and the mixture adjusted to pH of 4 by the addition of acetic acid. The mixture was then kept at 45 C. until the. reaction was complete.

4.5 moles of formaldehyde was then added to the above mixture as 37% formalin solution. The pH was adjusted to 5-5.5 and the mixture heated to 80 to 90 C. for about 4 hours. The mixture was then stripped of excess formaldehyde, leaving a thick viscous liquid identified as a methylolated ureidopyrimidone. The product at 50% solids contained about 10.5% nitrogen and had a Brookfield viscosity at 20 C. of 2.56 poises.

1,3 dimethyl0l-4-uredio-6-methyl-tetrahydro-Z-pyrimidone (B).-2 moles of urea was combined with 1 mole of crotonaldehyde and the mixture adjusted to pH 4 by the addition of phosphoric acid. This mixture was kept at 45 C. until the reaction was complete.

4.5 moles of formaldehyde was then added to the above mixture as paraformaldehyde of 37% formalin solution. The pH was adjusted to 3.5 to 5.5 and the mixture heated to 80 to 90 C. for about 4 hours. The mixture was then stripped of excess formaldehyde, leaving a thick viscous liquid identified as a methylolated methyl ureidopyrirnidone. The product at 50% solids contained 9.7% nitrogen and had a Brookfield viscosity at 20 C. of 120 poises.

Theamounts of the above ureidopyrimidones added to the viscose solution, regenerating solution or to the regenerated cellulose treating bath will vary widely; however, from about 0.1 to by weight of the cellulose is employed in the viscose (xanthate) solution. The regenerating (coagulation) bath or final product treatment bath will contain from 0.1 to 10% by weight based on the total weight of the bath. Stated another way, the finished regenerated cellulose product, i.e., cellulose film (cellophane) or cellulose fiber (rayon) will usually contain from 0.1 to 5% by weight of the ureidopyrimidone based on the total cellulose product and, preferably, from about 0.25 to 2% by weight.

The methylolated ureidopyrimidones are preferably added to the viscose solution after it has been allowed to ripen, but can be added at any time after its formation. The ureidopyrimidones may also be added with the coagulant, and as noted hereinbefore, they may also be applied to the formed or finished rayon or cellophane product as by dipping, spraying, painting and the like. The addition may be made by merely adding the ureidopyrimidones per se or a solution thereof to the viscose solution or by using the additive in combination with the coagulant. The addition can be made at any temperature, but is preferably made at or near room temperature.

The resulting viscose solution containing the added polymer is then subjected to conventional coagulation techniques to form the desired regenerated cellulose product. Coagulants that may be used for this purpose include the acids and acid salts such as sulfuric acid, hydrochloric acid, sodium bisulfate and the like.

The viscose solutions may be used to prepare a variety of products, such as filaments, cellulose films, coatings, plastic products, and the like. The formation of such products can be by the conventional techniques generally used for the formation of such regenerated cellulose products.

To illustrate the manner in which the invention may be carried out, the following examples are given. It is to be understood, however, that the examples are for the purpose of illustration and the invention is not to be regarded as limited to any of the specific materials or conditions recited therein.

Example I This example illustrates the treatment of finished cellophane with 1,3 dimethylol-4-ureido-6-methyl-tetrahydro-2-pyrimidone to improve its tensile strength.

Unplasticized cellophane (8 /2 x 11 inches) sheets were dip treated with a 10% by weight solution of 1,3-dirneth ylol-4-ureido-6-methyl-tetrahydro-2-pyrimidone. The cellophane sheets were air dried under slight tension (-10 g./cm.) and then cured in an air oven for 3 minutes at C. After conditioning for 24 hours (minimum) at 73 F. and 50% relative humidity, tensile strengths were determined on /2-inch strips. For wet tensile strengths the strips were placed in the clamps, sprayed with water and the tensile strength determined after 30 seconds. Comparative results were as follows (sheet thickness, approximately 1 mil):

Tensile Strength, lbs/in.

Dry Wet Example II This example illustrates the treatment of cellophane wherein 1,3 dimethylol-4-ureido-6-methyl-tetrahydro-Z- pyrimidone is added to the regeneration bath.

Viscose solutions were prepared by treating a commercial cellulose (Ul-tranier J.) with 18% sodium hydroxide solution and CS to obtain cellulose xanthate.

A regenerating solution was prepared which contained 10% H 50 18% NaSO 5% glucose and 1% ZnSO To this regenerating solution was then added 5% 1,3- dimethylol 4 ureido-6-methyl-tetrahydro-2-pyrimidone based on the bath.

Films were prepared by drawing a 14 mil doctor blade over a glass plate on which a suitable quantity of the viscose solution (6.7% cellulose) had been placed. The films supported on the plate were then placed in the modified regeneration bath at 50 C. for approximately 2 min utes. The treated cellophane films were dried by placing between two sheets of paper towels and placed on a drum dryer at 230 F. for 2 passes (6 minutes). After conditioning for at least 24 hours at 73 F. and 50% relative Tensile Strength, lbs./in., 0.001 inch sheet Dry Wet Cellophane prepared using unmodified regenerating bath 5. 1. 3 Cellophane prepared using a regenerating bath containing 1,8-dimethylol-4-ureido- 6-methy1tetrahydro2-pyrimidone 8. 6 1. 4

Example III This example illustrates the treatment of cellophane wherein the 1,3-dimethylol-4-ureido-6-methyl-tetrahydro- 2-pyrimidone is added to the viscose solution.

A viscose (xanthate) solution containing 6.7% cellulose was prepared as in Example II. To this solution was added 1,3 dimethylol-4-ureido-6-methyl-tetrahydro-Q-pyrimidone (2% by weight based upon the cellulose content). Films were prepared and treated with the unmodified regenerating solution as in Example II. Related improved results were obtained 'when 1,3-dimethylol-4- ureido-6-methyl-tetrahydro-2-pyrimidone was added to the xanthate solution.

Example IV The procedures of Examples I, II and III were substantially repeated wherein the methylolated ureido-pyrirnidone is 1,3-dimethylo1-4-ureido-tetrahydro-Z-pyrimidone. Similar improved wet and dry tensile strengths are obtained.

I claim as my invention:

1. A method for improving the tensile strength of regenerated cellulose products comprising adding from 0.1 to 10% by weight based on the cellulose content of a methylolated ureidopyrimidone having the general formula:

wherein n is 0 to 5, Y is selected from the group consisting of oxygen or sulfur, R is selected from the group consisting of hydrogen or alkyl radicals and X is selected from the group consisting of hydrogen, alkyl and alkylol groups at any step during the preparation of said cellulose or to the finished product thereof.

2. A method of improving the tensile strength of regenerated cellulose products comprising adding from 0.1 to 10% by weight of a methylolated ureidopyrimidone having the general formula:

wherein n is 0 to 5, Y is selected from the group consisting of oxygen or sulfur, R is selected from the group consisting of hydrogen or alkyl radicals and X is selected from the group consisting of hydrogen, alkyl and alkylol groups based on the cellulose content of the viscose solution to said viscose solution.

3. The method of claim 2 wherein the methylolated ureidopyrimidone is 1,3-dimethylol-4-ureido-6-methyltetrahydro-Z-pyrimidone.

4. The method of claim 2 wherein the methylolated ureidopyrimidone is 1,3-dimethylol-4-ureido-tetrahydro-2- pyrimidone.

5. A method for improving the tensile strength of regenerated cellulose products comprising adding from 0.1

to 10% by weight of a methylolated ureidopyrirnidone having the general formula:

wherein n is 0 to 5, Y is selected from the group consisting of oxygen or sulfur, R is selected from the group consisting of hydrogen or alkyl radicals and X is selected from the group consisting of hydrogen, alkyl and alkylol groups to the regenerating bath solution.

6. The method of claim 5 wherein the methylolated ureidopyrimidone is l,3-dimethylol-4-ureido-6-methyltetrahydro-2-pyrimidone.

7. The method of claim 5 wherein the methylolated ureidopyrimidone is 1,3-dimethylol-4-ureido-tetrahydro-2- pyrimidone.

8. A method for improving the tensile strength of regenerated cellulose products comprising contacting said cellulose products with a 0.1 to 10% by weight solution of a methylolated ureidopyrimidone having the general formula:

wherein n is 0 to 5, Y is selected from the group consisting of oxygen or sulfur, R is selected from the group consisting of hydrogen or alkyl radicals and X is selected from the group consisting of hydrogen, alkyl and alkylol groups.

9. The method of claim 8 wherein the methylolated ureidopyrimidone is l,3-dimethylol-4-ureido-6 methyltetrahydro-Z-pyrimidone.

10. The method of claim 8 wherein the methylolated ureidopyrimidone is l,3-dimethylol-4-ureido-tetrahydro-2- pyrimidone.

11. A regenerated cellulose product having improved tensile strength comprising from 0.1 to 5% by weight of a methylolated ureidopyrimidone having the general formula:

wherein n is 0 to 5, Y is selected from the group consisting of oxygen or sulfur, R is selected from the group consisting of hydrogen or alkyl radicals and X is selected from the group consisting of hydrogen, alkyl and alkylol groups.

7 '8 12. The cellulose product of claim 11 wherein the 15. Acellophane having improved tensile strength commethylolated ureidopyrimidone is 1,3-dimethylol-4-u1'eid0- prising from 0.1 to 5% by weight of 1,3-dimethyl01-4- 6-methy1-tetrahydrc-Z-pyrimidone. ureido-6-methyl-tetrahydro-2-pyrimidone.

13. The cellulose product of claim 11 wherein the methylolated ureidopyrimidone is 1,3-dimethylol-4-ureido- 5 NO refe e es Ci e tetrahydro-2-pyrimid0ne.

14. The cellulose product of claim 11 wherein the JULIUS FROME, Primary Examinermethylolated ureidopyrimidone content is from 0.25 to 2% by weight. 

1. A METHOD FOR IMPROVING THE TENSILE STRENGTH OF REGENERATED CELLULOSE PRODUCTS COMPRISING ADDING FROM 0.1 TO 10% BY WEIGHT BASED ON THE CELLULOSE CONTENT OF A METHYLOLATED UREIDOPYRIMIDONE HAVING THE GENERAL FORMULA: 